XSVCD
eXtended SVCD - XSVCD has same features as SVCD but it is possible to use higher bitrates and higher resolution to get higher video quality. XSVCD is basically everything that uses MPEG-2 video, is not within the SVCD standard or close to DVD , and burned in "SVCD" Mode on a CD-R or CD-R(W). XSVCD can be played on some hardware DVD players and many computers with appropriate software like a software DVD player or a media player with a MPEG-2 codec . VCDHelp X(S)VCD Info
XVCD
eXtended VCD - XVCD has same features as VCD but it is possible to use higher bitrates and higher resolution to get higher video quality. XVCD is basically everything that uses MPEG-1 video, is not within the VCD standard, and burned in "VCD" Mode on a CD-R or CD-R(W). XVCD can be played on some hardware VCD or DVD players and many computers with appropriate software. VCDHelp XVCD Info
XviD
XviD is an ISO MPEG-4 compliant video codec. It's not a product but an open source project which is developed and maintained by people around the world. XviD.org